So I'm trying to make something like a surf ramp in my map. It basically consists of a bunch of small triangular ramp slabs, which I then slanted at precise angles using the vertex tool. But when I compile it, close and then re-open Hammer, a whole bunch of the vertices have moved a few Hammer Units out of place. Am I just being over zealous with my ramp? Do I need to merge the vertices of adjacent ramp slices? How do surf maps do it?

You are probably making invalid geometry. (faces that end up not being flat). Once you've made stuff like this its easy to check by using CTRL+P (should bring up the general problem identifier window), and look for any invalid geometry errors.

As for them all moving, it probably just auto fixes the brushes... but i cant imagine why it would, normally it would just fail to compile

One thing about making surf ramps in hammer: don't use vertex edit to shape your ramps. You're better off clipping instead, because of the odd angles surf ramps are placed. Easier that way too. You can use the vertex edit tool to move your ramps, snap them into place onto the grid or zoom all the way in and alt+drag to disable snap and perfectly line them up, but when it comes to shaping and brush torture, hammer won't understand what you're trying to do and render it with a primitive algorithm. Probably the easiest way to make surf ramps is deciding how much of a curve you want to your ramp; and depending on how loose or tight it is, determines how wide or narrow you'd want each section. Rotate each section 5 degrees, then just shift+drag to make a copy. Take your copy then line up the outer most vertexes with the one you made the copy of. Magic.

This is the method i use, there is at least like 3 or 4 different ways to do it, it seems. This method is kinda lazy because I never bothered to line the ramps up perfectly, just overlapped em a tiny smidge.

-disregard the playerclips, the first rotation is supposed to say "-45" and its not the only method, but it works-

D'oh! Invalid geometry. I should've seen that coming. I just kinda assumed that because it rendered in Hammer it would render in game.

Deleted the ramp, and instead used the link NastyButler had, but I ended up doing pretty much exactly what Big Blue said. Works beautifully now.Learning more and more about mapping every time I make a new jump. This is awesome!

This is the method i use, there is at least like 3 or 4 different ways to do it, it seems. This method is kinda lazy because I never bothered to line the ramps up perfectly, just overlapped em a tiny smidge.

-disregard the playerclips, the first rotation is supposed to say "-45" and its not the only method, but it works-

I think using the vertex tool and moving it all onto the correct axis would be easier :]